This invention relates to a process for recovery of vanadium and molybdenum values from a feed material by solvent extraction of both vanadate and molybdate anions, said process comprises contacting under effective pH conditions an aqueous solution comprising molybdate and vanadate anions with a quaternary ammonium surfactant dissolved in an organic solvent immiscible with water and partitioning an extract phase rich in vanadate anions from a raffinate phase rich in molybdate anions. More particularly, this invention relates to a process for recovery of vanadium and molybdenum values from catalytic materials by solvent extraction of both vanadate and molybdate anions in a leachate solution from said catalytic materials, said process comprises contacting under effective pH conditions an aqueous alkaline solution of molybdate and vanadate ions with a trifatty monoalkyl quaternary ammonium salt dissolved in an organic solvent immiscible with water and partitioning an extract phase rich in vanadate anions from a raffinate phase rich in molybdate anions.
The metal vanadium is a strategically important metal for the United States and is not currently produced in the United States in any sizeable quantity. Important applications of vanadium include use as an alloying component in stainless steels and as a hardener in carbon steels and tool steels. Presently there is also a great deal of interest in upgrading petroleum resid feedstocks by hydroprocessing which gives rise to deposition of vanadium and nickel sulfides on hydroprocessing catalysts. For a typical resid feed with 200 ppm vanadium it is estimated that a major refinery processing 100,000 barrels of resid per day will accumulate 6,000 pounds per day of vanadium on the hydroprocessing catalyst. Recovery of this vanadium could provide about 15 percent of the U.S. requirements for vanadium.
Commercial extraction of vanadium and molybdenum from a feed material containing sulfides of both metals has typically been carried out by oxidizing the metal sulfides in the feed material to metal oxides and sulfates, followed by leaching the vanadate and molybdate anions from the material with an alkaline solution, recovering the alkali metal vanadate and molybdate from the alkaline solution, and separating vanadate from molybdate anions by fractional precipitation (see Toida et al., U.S. Pat. No. 4,145,397). This fractional precipitation method requires a lengthy, involved procedure, and large amounts of relatively expensive precipitating agents are necessary to obtain adequate product purity.
Several U.S. patents have disclosed extraction methods for recovery of metals such as molybdenum, rhenium, and vanadium from feed materials; and these extraction processes use extractants comprising quaternary ammonium surfactants and various amine based solutions (see Peterson, U.S. Pat. No. 3,251,555; Mollerstedt and Backius, U.S. Pat. No. 4,000,244; and Pitts, U.S. Pat. No. 4,150,092). However, none of these patents disclose the use of quaternary ammonium surfactants to perform extraction of both molybdate and vanadate anions from an alkaline leachate solution and at the same time carry out the single step separation of molybdate from vanadate anions.
While an extraction process for the recovery of both molybdate and vanadate anions by a quaternary ammonium surfactant solution has been disclosed by Lewis and Drobnick in U.S. Pat. No. 3,083,085, the patentees do not disclose the extraction and separation of molybdate and vanadate from each other. Moreover our studies have shown that the patentees' disclosed "optimum pH" values for extraction of 9.3 to 9.5 results not only in vanadate extraction, but also yields a large amount of molybdate in solution with the vanadate. Accordingly, there is a need for an improved extraction recovery process which will permit efficient extraction of molybdate and vanadate anions from an aqueous solution and will produce at least two separate products streams, each of high purity in vanadate or molybdate anions.
The general object of this invention is to provide an improved process to recover, separately, vanadium and molybdenum values from a feed material by a solvent extraction treatment of a solution containing vanadate and molybdate anions. A more specific object of this invention is to provide an improved process to recover, separately, vanadium and molybdenum values present on petroleum catalytic materials. Other objects of this invention will be apparent to persons skilled in the art from the following description and appended claims.